Several methods for high-resolution single photon emission computed tomography (SPECT) instrumentation to image awake, un-anesthetized small animals are currently available. As a result, functional imaging studies can now be performed on animals without anesthetics or significant restraints which could alter the results. The technology can be extended directly to clinical applications on human patients unable to remain still (e.g. Parkinson's patients, Alzheimer's patients, small children, etc.) during a scan.
In general, such methods rely on an optical measurement and motion tracking system that provides 3D position and orientation (pose) of a subject during the SPECT imaging scan. Typically, most methods rely on the use of external markers for motion tracking and pose calculation. While this approach has been proven to be accurate, the additional handling required to attach the markers is undesirable, particularly in animals. Further, markers and other similar devices can also be uncomfortable and can lead to additional motion of a subject with possible complete dislodgement of a marker/markers during the course of the scan.